Ensuring subprocesses are dead on exiting Python program

Question

Is there a way to ensure all created subprocess are dead at exit time of a Python program? By subprocess I mean those created with subprocess.Popen().

If not, should I iterate over all of the issuing kills and then kills -9? anything cleaner?

Answer 1

You can use atexit for this, and register any clean up tasks to be run when your program exits.

atexit.register(func[, *args[, **kargs]])

In your cleanup process, you can also implement your own wait, and kill it when a your desired timeout occurs.

>>> import atexit >>> import sys >>> import time >>>  >>>  >>> >>> def cleanup(): ...     timeout_sec = 5 ...     for p in all_processes: # list of your processes ...         p_sec = 0 ...         for second in range(timeout_sec): ...             if p.poll() == None: ...                 time.sleep(1) ...                 p_sec += 1 ...         if p_sec >= timeout_sec: ...             p.kill() # supported from python 2.6 ...     print 'cleaned up!' ... >>> >>> atexit.register(cleanup) >>> >>> sys.exit() cleaned up! 

Note -- Registered functions won't be run if this process (parent process) is killed.

The following windows method is no longer needed for python >= 2.6

Here's a way to kill a process in windows. Your Popen object has a pid attribute, so you can just call it by success = win_kill(p.pid) (Needs pywin32 installed):

    def win_kill(pid):         '''kill a process by specified PID in windows'''         import win32api         import win32con          hProc = None         try:             hProc = win32api.OpenProcess(win32con.PROCESS_TERMINATE, 0, pid)             win32api.TerminateProcess(hProc, 0)         except Exception:             return False         finally:             if hProc != None:                 hProc.Close()          return True 

Answer 2

On *nix's, maybe using process groups can help you out - you can catch subprocesses spawned by your subprocesses as well.

if __name__ == "__main__":   os.setpgrp() # create new process group, become its leader   try:     # some code   finally:     os.killpg(0, signal.SIGKILL) # kill all processes in my group 

Another consideration is to escalate the signals: from SIGTERM (default signal for kill) to SIGKILL (a.k.a kill -9). Wait a short while between the signals to give the process a chance to exit cleanly before you kill -9 it.